2.4 Electrode, Electrode Potential and Electrochemical Series

To understand how batteries and electrochemical cells work, we need to understand what happens when a metal is placed in a solution of its own ions. This creates an electrode and gives rise to an electrode potential. The relative values of these potentials allow us to arrange elements in an electrochemical series, which helps predict the direction of redox reactions and the voltage of a cell.

Main Idea

The main idea is that different metals have different tendencies to lose or gain electrons. When a metal is placed in water or a solution of its ions, a dynamic equilibrium is established between the metal atoms and their ions. This equilibrium creates a potential difference (voltage) between the metal and the solution. By measuring these potentials relative to a standard reference, we can rank the metals by their reactivity.

Core Concept

The core concept is the electrode potential. It is a measure of the tendency of a half-cell to undergo reduction. A more positive electrode potential means a greater tendency to be reduced (to gain electrons). A more negative electrode potential means a greater tendency to be oxidized (to lose electrons). This is why metals like zinc, with a negative potential, are good reducing agents, while ions like copper(II), with a positive potential, are good oxidizing agents.